1. Field of the Invention
The present invention is directed to a method and apparatus for the acquisition and display of a medical instrument that is introduced into a cavity organ of a patient to be examined or treated, particularly in the framework of a cardial examination or treatment with a catheter.
2. Description of the Prior Art
Examinations or treatments of patients are ensuing in minimally invasive procedures to an increasing degree, i.e. with the lowest possible operative outlay. Examples are treatments with endoscopes, laparoscopes or catheters that are respectively introduced into the examination region of the patient via a small body opening. Catheters are frequently utilized in the framework of cardiological examinations, for example in the case of arrhythmias of the heart that are currently treated by ablation procedures.
Under X-ray supervision, i.e. with the acquisition of fluoroscopic images, a catheter is thereby guided into a heart chamber via veins or arteries. In the heart chamber, the tissue causing the arrhythmia is ablated by applying high-frequency current, resulting in the previously arrhythmogenic substrate being left as necrotic tissue. The therapeutic character of this method exhibits great advantages compared to lifelong medication; moreover, this method is also economical in the long view.
A problem associated with such a procedure from a medical/technical point of view is that although the catheter can be visualized very exactly and highly resolved during the X-ray supervision in one or more fluoroscopic images—also called fluoro images—during the intervention, the anatomy of the patient can be imaged only very inadequately in the fluoroscopic images during the intervention. For tracking the catheter, conventionally two 2D fluoroscopic exposures are made from two different projection directions that primarily reside orthogonally relative to one another. On the basis of the visual information of these two exposures, the physician must then determine the position of the catheter on the basis of the physician's own perception, which is often possible only to a relatively imprecise degree.
U.S. Pat. No. 5,409,000 discloses the employment of an ablation catheter with integrated 2D-US (ultrasound) imaging in conjunction with a balloon-like mapping system, wherein the “arms” of the mapping system can be determined by the 2D-US imaging.
German OS 44 18 868 discloses an intravascular ultrasound catheter (IVUS) that is suited only for the US acquisition of vessels since only cross-sectional images of vessels can be generated. Here as well, the 3D reconstruction of the vessel ensues only on the basis of the position of the catheter tip, which is simply moved through the vessel.
U.S. Pat. No. 6,216,027 discloses the localization of catheters whose 3D position is identified with the assistance of ultrasound sensors.
German OS 40 21 102 discloses an apparatus wherein a 2D-US image is combined with a 2D X-ray image in that the US sensor is fixed relative to the X-ray C-arm system with the assistance of an articulated arm (with angle sensors).
U.S. Pat. No. 5,016,642 discloses that slow motion of a beating heart be visualized with the assistance of 2D-US.
U.S. Pat. No. 5,125,410 discloses a purely IVUS vessel application, whereby only 2D-US cross-sectional images of vessels are employed.